Several communication systems use a shared medium for exchange of information. Examples of such communication systems include HomePlug AV based powerline communication systems, IEEE 802.11 based wireless communications systems and DOCSIS based cable modem system. Due to the shared nature of the medium, signals transmitted in these systems can also be received by unauthorized device. To protect privacy and to prevent rogue devices from accessing the network, these systems incorporate security. Secure systems use authorization process to determine if the device can be admitted into the network. Remote authentication dial in user service (RADIUS) is an example of common authorization system. Authorized devices are provided with the encryptions keys that are used to encryption information transmitted over the medium, thus protecting privacy of the information. Advanced Encryption Standard (AES) is another encryption mechanism used by various communication systems.